In reply to mikenty:
> A couple of pigs would clear the area pretty quickly, but may not be practical for you!
It's not that large an area. I reckon one pig could do it in a day, if sufficiently motivated. And we like pigs! Perhaps we could borrow one for a day or two - maybe in return for a few sausages when it undergoes its "career change"...
The plan is to replace the 'manicured' grass with a bit of wildflower 'meadow'. It doesn't matter if it all ends up looking a bit raggy because it's largely out of sight behind the summerhouse, but past experience suggests that you need to extirpate the existing grass otherwise the new seed won't take.
As a slight complication: there's a hawthorn smack bang in the middle of the area in question. We planted it ourselves a few years back so we don't want to lose it, or risk damaging it.